Maybe it was wishful thinking or even naivete, he speculated later, but when Zach Walters was called into his manager’s office in South Bend, Ind., on Friday, July 30, his heart sank.

Traded? How could he be traded? He had been drafted by the Arizona Diamondbacks a little more than a year before. Being a Diamondback for life was how he envisioned it — how every minor leaguer probably envisions it, he thought.

His mind raced as his manager, Mark Haley, told him the details: He was headed to Washington — to Woodbridge, Va., and the Potomac Nationals more specifically — as part of a trade for veteran starter Jason Marquis.

“OK,” Walters said, digesting the news, knowing his next question was an important one. “So who else was traded with me?”

There was no scenario the Montana native, Las Vegas resident and University of San Diego graduate could fathom that involved him, a low Single-A infielder, being traded straight-up for an established major leaguer like Marquis.

Except that he was.

“God, I’ve got to do great,” Walters remembered telling himself. “I’ve got to hit .900 with 37 home runs in the first week.”

As he thought back to that day from the sun-drenched fields of the Arizona Fall League — one of the last places he expected to spend October and most of November — he chuckled at the immense pressure he felt when he first became a National.

“It would have been great,” he said of his goals to put up impossible numbers. “I think I ended up hitting like .190 the first week.”

The 22-year-old finished the season hitting an even .300, though, with a .367 on-base percentage and .457 slugging percentage between his time in South Bend at low-A and with high-A Potomac. The more the Nationals saw of him, the more it became clear that this may not be the proven-major-leaguer-for-prospect dump that most shrugged it off as at first. Walters is versatile — a true shortstop who is solid at second base and third base, played center field in college and is learning the corner outfield spots — and his potential is high.

“There’s no shortstop that’s a real shortstop that will tell you he’s something else,” Walters said. “But I’ve got to show them I can play it all. I have no problem with that. … As long as I get to hit, I don’t have a problem. I’d play catcher if I could.”

As he acclimated himself to the Arizona Fall League, taking grounders all over the infield and fly balls in the outfield each day, scouts buzzed about his potential, though he tailed off offensively with a .205 average. The comparisons weren’t to superstars, but the names of Jerry Hairston Jr. and Brian Bixler were bandied about — their versatility and capability at a multitude of spots a mold many saw Walters fitting.

“He doesn’t come with a lot of the publicity or fanfare but he’s been a really steady performer in the short time he’s been in pro baseball,” said Nationals director of player development Doug Harris. “We pushed him to a more advanced league and he struggled a little early — which is normal — but made a quick adjustment, which really speaks volumes to his ability, and finished very strongly.”

So strongly that when the team’s top 2011 draft pick Anthony Rendon was deemed unready for the AFL, Walters was the one whose bags were packed at the Nationals minor league complex in Viera, Fla.

“I’m really happy here,” said Walters, who was reunited at Potomac with former USD teammates Sammy Solis and Sean Nicol. “It’s a big family, that’s all it is. When you don’t take out the trash or get bad grades on your report card, they let you know. But it’s really a big family.”

That’s a feeling Walters is familiar with, his own family making sacrifices for his baseball aspirations throughout his childhood. They moved to Las Vegas for his high school years so he could play in leagues alongside Bryce Harper, who was playing above his age, and he spent his time at the University of San Diego wisely enough to graduate in three years, with assistance from University of Nevada-Las Vegas online summer courses. That way, when he was at USD he could focus on baseball with the likes of Orioles pitcher Brian Matusz and Solis — going 2-for-4 (with two singles and two strikeouts) against “a video-game-like” Stephen Strasburg during the future No. 1 pick’s time at San Diego State.

So he fit when he arrived in Potomac, the familiar faces helping him adjust and his quick wit and wry sarcasm making it an easier transition. His goal is to start the 2012 season at Double-A — a continued progression in what will be just his third minor league season. Maybe down the road he’ll begin to see Jason Marquis as the pitcher who was traded for him, instead of the other way around.

“[The trade] was just havoc,” Walters said. “But every guy gets traded or plays with a different team along the way. At first I was kind of like, ‘[Shoot], they hate me. I’m going down the drain,’ and then I just realized everything would be fine.”